1. Field of the Invention
The present invention relates to a wireless adhoc communication system. More particularly, the present invention relates to a wireless adhoc communication system for performing communication while confirming among devices that a frame is transmitted from an authenticated terminal, a terminal for use in a system, an authentication method, an encryption method, a terminal management method for use in the system and the terminal, and a program for enabling a computer (terminal) to perform those methods.
2. Description of the Related Art
As electronic devices have become smaller, have come to have higher performance, and have become easy to use while being carried, there has been a demand for an environment in which a terminal is connected to a network in situ where necessary so as to make communication possible. In one of the environments, the development of a network which is temporarily constructed as necessary, that is, a wireless adhoc network technology, has been in progress. In this wireless adhoc network, terminals (for example, PDAs (Personal Digital Assistants), and cellular phones) are interconnected with one another in an autonomously distributed manner without providing a specific access point.
In a conventional wireless LAN (Local Area Network) environment, since a specific access point is provided and wireless communication is performed between that access point and the terminal, encryption of frames in a wireless zone thereof will suffice. For example, in WEP (Wired Equivalent Privacy) in the encryption specification of wireless LAN, frames are encrypted in advance using an encryption key, and when the frames are decrypted at the access point, by performing CRC (Cyclic Redundancy Check), frames from a terminal which is not authenticated is discarded (for example, refer to Japanese Unexamined Patent Application Publication No. 2001-111544 (FIG. 3)).
Although, in the above-described wireless LAN, the wireless zone is limited to the section between the access point and the terminal, in the wireless adhoc communication system, the entirety of the network topology is formed by a wireless medium. Therefore, since, in the wireless adhoc communication system, there occurs a case in which frames are delivered by making a plurality of wireless links hop, there is a risk that, as a result of an encryption process and a decryption process being repeated for each wireless link, a load is incurred at each terminal, wasting the calculation resources. Furthermore, since the delivery of frames from a terminal which is not authenticated among a plurality of devices causes an originally unwanted communication to occur, there is a risk that the wireless resources are wasted.